lib/dnspython/dns/ipv6.py

   1 # Copyright (C) 2003-2007, 2009-2011 Nominum, Inc.
   2 #
   3 # Permission to use, copy, modify, and distribute this software and its
   4 # documentation for any purpose with or without fee is hereby granted,
   5 # provided that the above copyright notice and this permission notice
   6 # appear in all copies.
   7 #
   8 # THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
   9 # WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  10 # MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
  11 # ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  12 # WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  13 # ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
  14 # OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  15
  16 """IPv6 helper functions."""
  17
  18 import re
  19
  20 import dns.exception
  21 import dns.ipv4
  22
  23 _leading_zero = re.compile(r'0+([0-9a-f]+)')
  24
  25 def inet_ntoa(address):
  26     """Convert a network format IPv6 address into text.
  27
  28     @param address: the binary address
  29     @type address: string
  30     @rtype: string
  31     @raises ValueError: the address isn't 16 bytes long
  32     """
  33
  34     if len(address) != 16:
  35         raise ValueError("IPv6 addresses are 16 bytes long")
  36     hex = address.encode('hex_codec')
  37     chunks = []
  38     i = 0
  39     l = len(hex)
  40     while i < l:
  41         chunk = hex[i : i + 4]
  42         # strip leading zeros.  we do this with an re instead of
  43         # with lstrip() because lstrip() didn't support chars until
  44         # python 2.2.2
  45         m = _leading_zero.match(chunk)
  46         if not m is None:
  47             chunk = m.group(1)
  48         chunks.append(chunk)
  49         i += 4
  50     #
  51     # Compress the longest subsequence of 0-value chunks to ::
  52     #
  53     best_start = 0
  54     best_len = 0
  55     start = -1
  56     last_was_zero = False
  57     for i in xrange(8):
  58         if chunks[i] != '0':
  59             if last_was_zero:
  60                 end = i
  61                 current_len = end - start
  62                 if current_len > best_len:
  63                     best_start = start
  64                     best_len = current_len
  65                 last_was_zero = False
  66         elif not last_was_zero:
  67             start = i
  68             last_was_zero = True
  69     if last_was_zero:
  70         end = 8
  71         current_len = end - start
  72         if current_len > best_len:
  73             best_start = start
  74             best_len = current_len
  75     if best_len > 0:
  76         if best_start == 0 and \
  77            (best_len == 6 or
  78             best_len == 5 and chunks[5] == 'ffff'):
  79             # We have an embedded IPv4 address
  80             if best_len == 6:
  81                 prefix = '::'
  82             else:
  83                 prefix = '::ffff:'
  84             hex = prefix + dns.ipv4.inet_ntoa(address[12:])
  85         else:
  86             hex = ':'.join(chunks[:best_start]) + '::' + \
  87                   ':'.join(chunks[best_start + best_len:])
  88     else:
  89         hex = ':'.join(chunks)
  90     return hex
  91
  92 _v4_ending = re.compile(r'(.*):(\d+\.\d+\.\d+\.\d+)$')
  93 _colon_colon_start = re.compile(r'::.*')
  94 _colon_colon_end = re.compile(r'.*::$')
  95
  96 def inet_aton(text):
  97     """Convert a text format IPv6 address into network format.
  98
  99     @param text: the textual address
 100     @type text: string
 101     @rtype: string
 102     @raises dns.exception.SyntaxError: the text was not properly formatted
 103     """
 104
 105     #
 106     # Our aim here is not something fast; we just want something that works.
 107     #
 108
 109     if text == '::':
 110         text = '0::'
 111     #
 112     # Get rid of the icky dot-quad syntax if we have it.
 113     #
 114     m = _v4_ending.match(text)
 115     if not m is None:
 116         b = dns.ipv4.inet_aton(m.group(2))
 117         text = "%s:%02x%02x:%02x%02x" % (m.group(1), ord(b[0]), ord(b[1]),
 118                                          ord(b[2]), ord(b[3]))
 119     #
 120     # Try to turn '::<whatever>' into ':<whatever>'; if no match try to
 121     # turn '<whatever>::' into '<whatever>:'
 122     #
 123     m = _colon_colon_start.match(text)
 124     if not m is None:
 125         text = text[1:]
 126     else:
 127         m = _colon_colon_end.match(text)
 128         if not m is None:
 129             text = text[:-1]
 130     #
 131     # Now canonicalize into 8 chunks of 4 hex digits each
 132     #
 133     chunks = text.split(':')
 134     l = len(chunks)
 135     if l > 8:
 136         raise dns.exception.SyntaxError
 137     seen_empty = False
 138     canonical = []
 139     for c in chunks:
 140         if c == '':
 141             if seen_empty:
 142                 raise dns.exception.SyntaxError
 143             seen_empty = True
 144             for i in xrange(0, 8 - l + 1):
 145                 canonical.append('0000')
 146         else:
 147             lc = len(c)
 148             if lc > 4:
 149                 raise dns.exception.SyntaxError
 150             if lc != 4:
 151                 c = ('0' * (4 - lc)) + c
 152             canonical.append(c)
 153     if l < 8 and not seen_empty:
 154         raise dns.exception.SyntaxError
 155     text = ''.join(canonical)
 156
 157     #
 158     # Finally we can go to binary.
 159     #
 160     try:
 161         return text.decode('hex_codec')
 162     except TypeError:
 163         raise dns.exception.SyntaxError